The ratio of wavelengths for transition of electrons from $$2^{\text {nd }}$$ orbit to $$1^{\text {st }}$$ orbit of Helium $$\left(\mathrm{He}^{++}\right)$$ and Lithium $$\left(\mathrm{Li}^{++1}\right)$$ is (Atomic number of Helium $$=2$$, Atomic number of Lithium $$=3$$ )

For an intrinsic semiconductor $$\left(\mathrm{n}_{\mathrm{h}}\right.$$ and $$\mathrm{n}_{\mathrm{e}}$$ are the number of holes per unit volume and number of electrons per unit volume respectively)

A $$5.0 \mathrm{~V}$$ stabilized power supply is required to be designed using a $$12 \mathrm{~V}$$ DC power supply as input source. The maximum power rating of zener diode is $$2.0 \mathrm{~W}$$. The minimum value of resistance $$R_{\mathrm{s}}$$ in $$\Omega$$ connected in series with zener diode will be

A jar '$$\mathrm{P}$$' is filled with gas having pressure, volume and temperature $$\mathrm{P}, \mathrm{V}, \mathrm{T}$$ respectively. Another gas jar $$Q$$ filled with a gas having pressure $$2 \mathrm{P}$$, volume $$\frac{\mathrm{V}}{4}$$ and temperature $$2 \mathrm{~T}$$. The ratio of the number of molecules in jar $$\mathrm{P}$$ to those in jar $$Q$$ is